The present invention pertains to printed wiring boards and more particularly to preventing solder defects from wave soldering of printed wiring boards.
Printed circuit boards (PCBs) or printed wiring boards (PWBs) are employed in the electronics industry for the placement and interconnection of electronic circuits. These electronic circuits may comprise dual in-line packages of the surface mount type or those with leads which penetrate the printed wiring board through holes or apertures in the board. These dual in-line packages whether surface-mount or hole-mount type are typically connected electrically to the printed wiring board via a mass soldering operation since there may be a great number of these DIP packages on a printed wiring board. The mass soldering process may include wave soldering applications. The dual in-line packages have two rows of closely spaced leads.
In the wave soldering process, the printed wiring board, to which the electrically components are affixed, is drawn or pulled through a wave of solder. The components are affixed to the board by gluing surface-mounted devices and by inserting hole-mount devices into the appropriate holes in the printed wiring board. The printed wiring board has previously been affixed with solder pads in the case of surface-mount components or solder pads surrounding the holes in which the components have been placed. The printed wiring board is pulled through a wave of solder which covers the components and causes the solder pads to be reflowed to make electrical connection between the printed wiring board and the electrical circuit components (DIPs). As the printed wiring board is drawn through the solder wave, solder bridges are formed between the last two leads of each row of leads. Such solder bridges provide a short circuit between these leads and are therefore defects.
For DIP packages which are inserted through holes in the PWB, it has been found that adding an extra solder pad in-line at the end of each line of leads for the DIP package causes the solder in the wave soldering process to be drawn to the extra solder pad and form a bridge between the last functional lead in each line of leads and the functionally useless extra solder pad.
What is needed is a solder thief for preventing bridging between leads of dual in-line packages while providing electrical interconnection of these leads to other layers or surfaces of the printed wiring board.